1. Field of the Invention
The present invention relates to a lens-fitted photographic film unit and a method of manufacturing the same. More particularly, the present invention relates to a lens-fitted film unit with which a user can take more photographs than a standard number of the photographable frames of the strip of photographic film contained therein, and a method of manufacturing such a film unit.
2. Description Related to the Prior Art
A 135-type photographic filmstrip (hereinafter referred to as film) in a cassette as defined by ISO code 1007, 1979 version, is given a standard number of photographable frames and a length sufficient for such frames (ISO signifies International Organization for Standardization). A user takes photographs to expose a series of the standard number of frames on the film. There are, however, occasions on which a conventional camera happens to take on standard film one or two exposures in addition to the standard number of exposures. Because such a conventional camera is manually loaded with film by a user, it is impossible, after completing exposure of the film, to estimate with precision the position of the picture frame nearest to the film leader. Thus it cannot be known how much leader can be pulled out of a cassette for development without accidental exposure of a picture to ambient light. In consideration of this, the prevailing standard provides an allowance of film beyond the length sufficient for the nominal number of exposures.
The available length of the film is defined as the distance between the mouth of the cassette and the film leader when the film is fully drawn out of the cassette. As pointed out above, this available length is set to be longer than the series of the stated number of frames, and includes a lengthwise allowance to be left unexposed, which is approximately four times as long as a single frame. It is therefore possible in a camera to make on a film one to three exposures in addition to the stated number of exposures, which is dependent upon a manner of loading the camera with the film.
Lens-fitted photographic film units (hereinafter referred to simply as film units) are now on the market, e.g. under the trademark "Quick Snap" (manufactured by Fuji Photo Film Co., Ltd.). Such known film units are disclosed in e.g. U.S. Pat. Nos. 4,884,087 and 4,972,649, and are a single-use camera preloaded with photographic film. Such a film unit has a film housing of which a front cover and a rear cover are secured to a main body, in which body a taking lens, a film wind-up wheel and a shutter mechanism are incorporated. The main body is provided with a film supply chamber and a cassette-containing chamber formed on opposite horizontal sides of the taking lens. The unexposed film is wound in a roll in the film supply chamber. The externally rotatable wind-up wheel is engaged with a spool in the cassette contained in the film take-up chamber. A user who has purchased the film unit winds the film frame by frame back into the cassette after each exposure.
A driven sprocket wheel engages perforations in the film, and, when the film is wound up, is rotated by the moving film. When the film is wound up by one frame, namely eight perforations, responsive rotation of the sprocket causes a wind-up stopping mechanism to prevent the wind-up wheel from rotating further, cocks the shutter mechanism, and steps the count of a count-indicating wheel.
The film unit as manufactured must be inspected before it can be shipped, because the film unit should be usable with high reliability, without difficulties caused by manufacture of the film unit. It is usual to inspect the operation of the shutter mechanism. After the main body is loaded with the drawn-out film and its cassette, the shutter mechanism is cocked and then released, so as to check the operation.
There is a problem in this inspection of the film unit to be shipped. Cocking and releasing of the shutter mechanism for checking the operation must spend one frame of the film, with a length of eight perforations, and thus reduces the lengthwise allowance of the film available for possible exposures in addition to the stated number of photographable frames. If inspection other than the operation of the shutter of the film unit is performed, more than one frame will be spent.